I recently bought a 2001 slk 320. It has developed a "thunk" in the rear area (sounds like it is coming from the trunk) under the following conditions:
- car has been sitting awhile (at least 30 minutes, but typically several hours)
- happens ONCE when car reaches about 10 mph forward
- will not happen again until car has been parked for awhile (i.e. does not happen when I stop at a red light)
I took it to the dealer and they (finally) diagnosed it as a defective trunk latch, which they replaced. Well, needless to say, it still makes the noise. It must be something that is settling over time, or some kind of thermal effect.
Any ideas?
Thanks,
Becca

 

Hi Becca.
You may not be aware that your car has auto door locking. At approx. 10mph the doors lock and this creates a "Thunk" type noise as the latches fire. This function can be turned off if required. Instructions are in handbook.
Hope you got your money back from the dealer!
Let me know if this doesn't resolve your problem since I think my 320 may have a noise other than the auto central locking but will need to confirm.
Stuart

 

I also have the same clunky noise...

But, I am quite sure it is the auto locking system ( when over 10mph ).

Sometimes it does sound like something a bit more, but I think this is just an illusion
created by a over imaginative brain.

It's taken some getting used to, but now I just ignore it.

There are other clunks and rattles about though.

If the tool kit is not secure it sometimes makes the odd thunk or two.
And also make sure the jack unit and nut bar are secure.

Sometimes I'm sure the side window flaps make a noise when going round corners.

The most recent noise is the drivers side door rattles sometimes.
I am going to remove the panels to investigate as also when winding the window up there
is a scratching noise and the glass gets marked!

oh, another noise is the parking brake.
Put on the parking brake whilst on a slope and release the foot brake and the
car rolls back a few inches and you get a clunk. I think this is just a "feature" of the
parking brake system, as it does not operate the rear pads.

If anyone wants more on the problems I have found, I could list many more.....


Oh well,

Have fun, regards,

Mark

( Oh, I've finally got a quote for a new front bumper/ paint/fitting = £583 +vat! )